SAN FRANCISCO — In a quick reversal, Twitter rolled back most of the controversial changes it made to its “block” feature after a sharp outcry from users.

The mass protest on Twitter was the first for the San Francisco social network as a public company. Executives held an emergency meeting Thursday night to deal with the escalating situation.

Twitter users took to the service to protest under the hashtag #RestoreTheBlock. They said the changes to the block feature would encourage online abuse and harassment on the service. Many women in particular said they would no longer feel safe on Twitter, where they say they receive rape and other threats.

Under the original system, users could prevent people who were harassing them from following them and interacting with their tweets.

Under the new rules that Twitter rolled out Thursday, a blocked user could view the person’s tweets and tweet at the person.

Twitter said it was trying to protect victims of harassment from retaliation. But users did not see it that way.

In a blog post Thursday night, Michael Sippey, Twitter’s vice president of product, said: “We have decided to revert the change after receiving feedback from many users — we never want to introduce features at the cost of users feeling less safe. Any blocks you had previously instituted are still in effect.”

“In reverting this change to the block function, users will once again be able to tell that they’ve been blocked. We believe this is not ideal, largely due to the retaliation against blocking users by blocked users (and sometimes their friends) that often occurs. Some users worry just as much about post-blocking retaliation as they do about pre-blocking abuse. Moving forward, we will continue to explore features designed to protect users from abuse and prevent retaliation.”